KR20080073550A - Wireless lan system and transmission method of data thereof - Google Patents

Abstract

A wireless communication system and a data transmission method thereof are provided to schedule frame transmission order by considering delay time information of a transmitted frame, thereby first transmitting a retransmitted frame. Transmission time is stored in a transmission frame to be transmitted(S110). A transmission station sends the transmission frame(S120). The transmission station decides whether an ACK frame is received within designated time from a receiving station(S130). If not, user priority of the transmission frame is set by using delay parameters of the retransmitted transmission frame(S140). An AC(Access Category) is determined according to the user priority(S150). The transmission frame is forwarded to a transmission queue corresponding to the determined AC(S160).

Description

Wireless communication system and data transmission method thereof {Wireless LAN system and Transmission method of data among}

1 is a schematic diagram illustrating an EDCA channel approach.

2 is a schematic diagram showing a race condition for each AC in a station in the EDCA scheme.

3 is a schematic diagram illustrating EDCA TXOP bursting.

4 is a block diagram showing the structure of an ACK frame;

5 is a block diagram illustrating a MAC header area of a transport frame according to a specific embodiment of the present invention.

6 is a flowchart illustrating a frame transmission method according to the first embodiment of the present invention.

7 is a flowchart illustrating a frame transmission method according to the second and third embodiments of the present invention.

8 is a flowchart illustrating a frame transmission method according to the fourth and third embodiments of the present invention.

The present invention relates to a frame transmission scheduling method for wireless communication in consideration of transmission delay time information of a frame.

Wireless LANs are widely used in a variety of wireless user environments, such as home networks, corporate wireless networks, and hot spots. The existing commercial wireless LAN is an extension of Ethernet and provides only Best Effort service based on IEEE 802.11b standardized in 1999. Wireless LAN users, however, want to deliver a complete multimedia stream without losing transmission data. New applications, especially video or multimedia streaming, require excellent quality of service (QoS) even in wireless LAN environments.

The constant user demand for bandwidth expansion has resulted in increased congestion of the entire wireless network and a decrease in relative transmission speeds. As a result, network managers need new mechanisms to ensure the service of applications that require strict QoS, even in high-congestion networks. This requirement eventually led to the development of improved Medium Access Control (MAC) protocols over traditional wireless LANs. .

802.11 MAC defines a mandatory function, Distributed Coordination Function (DCF) and an optional function, Point Coordination Function (PCF). That is, the transmission medium may operate in both DCF in contention mode and PCF in contention free mode. DCF is an asynchronous transmission method that provides the basic medium approach of 802.11 MAC and is implemented in all commercial wireless LAN products. DCF takes no account of the priority among stations (hereinafter referred to as 'STA') in wireless media access. These characteristics of DCF do not reflect the transmission of various types of data traffic, and thus cannot support QoS required by users.

Synchronous transmission is implemented by the PCF as a media approach through polling. The PCF uses a centralized polling function in which a point coordination (PC) function is located at a central access point (hereinafter referred to as an 'AP') to directly control services for all STAs by the AP. That is, the AP periodically polls the combined STAs to give each STA a chance to send a frame.

The existing 802.11 medium access control (MAC) has many problems in supporting wireless LAN quality of service (QoS). Distributed Coordination Function (DCF), an essential feature of 802.11 MACs, does not provide any function for QoS support. Therefore, when the DCF method is used, all data traffic is serviced in the order of arrival in the transmission queue and is processed in the best effort method.

Unlike DCF, Point Coordination Function (PCF) of 802.11 MAC was developed to support services for real-time traffic, but currently supports QoS.

That is, the PC (Point Coordinator) located in the AP in the PCF method defines a scheduling algorithm based on a simple round-robin method for polling. However, since there are various types of traffic that require differentiated QoS, the round robin algorithm that cannot prioritize traffic has a problem that is not sufficient to support this.

In addition, if the size of the super frame is small, repetition of the contention period and the contention free period may cause a significant overhead.

In addition, in the conventional MAC, the transmission of the beacon frame or the timing of the super frame may be changed. The PC prepares a beacon frame to be transmitted after the target beacon transmission time (TBTT), and transmits the beacon frame if the medium is spaced during the PISF (Point Inter Frame Space). However, although the STAs may not finish the frame transmission in the upcoming TBTT, there may be a problem that the transmission may be started, thereby delaying the beacon frame transmission.

The delay of the beacon frame to be transmitted immediately after the TBTT, in turn, delays the transmission of the tense frame that must be transmitted in the non-competition period. This problem causes a time delay that is unpredictable in a non-competitive cycle, which seriously affects QoS.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide frame delay time information to frame transmission scheduling in a contention-based channel access method for improving the quality of service of wireless communication. It provides a wireless communication system and a frame transmission method comprising the same.

Another object of the present invention is to allow a virtual collision handler to select a transmission frame based on frame delay time information as well as user priority when a collision between ACs changes, so that a retransmitted frame may be transmitted first. The present invention provides a wireless communication system and a frame transmission method thereof to prevent a transmission frame from being delayed for a long time.

According to a feature of the present invention for achieving the above object, the present invention stores the transmission time in the transmission frame, and calculates the delay time using the transmission time when the retransmission request for the transmission frame A transmission station for scheduling transmission of the transmission frame using the delay time; And a receiving station for transmitting an ACK frame to the transmitting station upon receiving the transmitting frame.

In this case, the transmission time may be stored in a delay parameter area provided in the MAC header portion of the transmission frame.

Meanwhile, in the scheduling of the transmission frame, a predetermined time range is divided into a plurality of groups, each group has an added value and a value, and the user priority is modified by modifying the user priority according to the added value of the group corresponding to the delay time. It may be performed based on the ranking.

The present invention further provides that if the modified user priority is less than zero, the user priority is set to zero; If the modified user priority is greater than 7, the user priority may be set to seven.

In the scheduling of the transmission frame, a delay level is set and stored from the delay time, AC is determined first based on user priority, and AC is adjusted in consideration of the delay level to determine a final AC to which the transmission frame belongs. It may be set.

Alternatively, the scheduling of the transmission frame determines whether the delay time exceeds a prescribed time, and if the delay time exceeds the prescribed time, allocates the transmission frame to a transmission queue corresponding to the best user priority. May be to be transmitted preferentially.

In the scheduling of the transmission frame, it is determined whether the delay time exceeds a prescribed time, and when the delay time exceeds a prescribed time, one step from the transmission queue corresponding to the user priority of the transmission frame. It may be to be assigned to the transmission queue with a higher priority to be transmitted.

The transmitting station may also be an access point, and the receiving station may be a terminal device.

The transmission frame may be a QoS data frame.

In this case, the wireless communication may be an ad-hoc mode, and the transmitting station and the receiving station may be terminal devices.

On the other hand, the present invention includes a transmission station for storing a transmission time in a transmission frame, and a virtual collision processor for selecting a frame to be transmitted using the delay time calculated from the transmission time when the collision between the AC and ; And a receiving station for transmitting an ACK frame to the transmitting station upon receiving the transmitting frame.

In this case, the virtual collision processor divides a predetermined time range into a plurality of groups, adds and subtracts a value to each group, modifies a user priority according to a priority table according to the value of the group corresponding to the delay time, The modified user priority may be compared to select and transmit a frame having the highest modified priority.

In addition, the virtual collision processor may determine whether the delay time exceeds a threshold value and, if there is a transmission frame having a delay time exceeding the threshold value, may select and transmit the transmission frame as the highest priority. .

In addition, the present invention provides a contention-based channel access method for improving the quality of service of a wireless communication, comprising: (A) storing a transmission time in a transmission frame to be transmitted; (B) transmitting the transmission frame; (C) checking whether a response frame is received within a designated time; (D) if the response frame is not received within a specified time, calculating a delay time from the transmission time, and setting a user priority of the transmission frame using the delay time; (E) determining an access category (AC) according to the set user priority; And (F) transmitting a frame to a transmission queue corresponding to the AC.

At this time, the setting of the priority in the step (D) is to divide the predetermined time range into a plurality of groups, and to put each of the groups with an added value, and according to the priority table according to the added value of the group corresponding to the delay time. Can be set by modifying the set user priority.

And (D ') if the user priority is less than zero, setting the user priority to zero; (D ″) if the user priority is greater than 7, the method may further include setting the user priority to 7.

In this case, the transmitting station may be an access point, and the receiving station may be a terminal device.

The transmission frame may be a QoS data frame.

Meanwhile, both the transmitting station and the receiving station may be terminal devices, and the wireless communication may be in an add-hoc mode.

In addition, the present invention provides a contention-based channel access method for improving the quality of service of a wireless communication, the method comprising: (a) storing a transmission time in a transmission frame to be transmitted; (b) transmitting the transmission frame; (c) checking whether a response frame is received within a designated time; (d) if the response frame is not received within a specified time, setting a user priority of the transmission frame according to a priority table; (e) determining an access category (AC) of the transmission frame using a delay time calculated based on the user priority and the transmission time; And (f) transmitting a transmission frame to a transmission queue corresponding to the AC.

In this case, the determining of the AC in the step (e) may be to calculate a delay level corresponding to the delay time and determine the AC to which the transmission frame belongs according to the delay level.

Alternatively, in step (e), the determination of the AC determines whether the delay time exceeds a prescribed time, and sets the transmission frame to belong to the highest AC when the delay time exceeds the prescribed time. It may be.

And, in step (e), the determination of the AC determines whether the delay time exceeds a prescribed time, and if the delay time exceeds a prescribed time, corresponding to the user priority of the transmission frame. The transmission frame may be allocated by an AC having a higher priority than AC.

In this case, the transmission time may be stored in a delay parameter area provided in the MAC header portion of the transmission frame.

On the other hand, the present invention provides a contention-based channel access method for improving the quality of service of a wireless communication, the method comprising the steps of: (I) storing the transmission time in a transmission frame to be transmitted; (II) transmitting the transmission frame; (III) detecting whether an internal collision between ACs has occurred; (IV) selecting, by the virtual collision processor, a frame to be transmitted in consideration of the transmission time when the internal collision occurs; (V) a method of transmitting a frame of wireless communication, the method comprising transmitting the set frame.

At this time, in step (IV), the transmission frame is selected by dividing a predetermined time range into a plurality of groups, and adding or subtracting a predetermined time range to each group, according to the priority table according to the added / decreased value of the corresponding group. The user priority may be modified, the modified user priority may be compared, and the frame having the highest modified priority may be selected and transmitted.

Or in step (IV), the selection of the transmission frame determines whether the delay time exceeds a threshold value, and if there is a transmission frame having a delay time exceeding the threshold value, the transmission frame has the highest priority. It may also be selected and transmitted.

On the other hand, the present invention comprises the steps of storing the received data in the data buffer according to the user priority; Storing a transmission time when transmitting the stored data; When transmitting the data, driving a timer to determine whether a response signal to the transmitted data is received before the timer reaches a specific value; Calculating a delay time for the data using the stored transmission time when the timer reaches a specific value without receiving the response signal; And setting a user priority of the data by using the calculated delay time, storing the data in a data buffer corresponding to the user priority, and then attempting to retransmit the data. It includes.

In this case, the user priority may be set when data to be transmitted is transferred from an upper layer to the MAC layer, and may be stored in the MAC header portion of the data.

The transmission time may be stored in a delay parameter area included in the MAC header portion of the data.

Also. The delay time may be set to 0 when the measured value of the timer is less than or equal to the default value, and may be a value exceeding the default value when the measured value of the timer exceeds the default value.

In this case, the setting of the user priority may be performed by dividing the delay time into a plurality of groups, adding and subtracting the delay time to each group, and adding or subtracting the user priority determined by the nature of the data to the group corresponding to the delay time. It may be set to be modified according to.

Alternatively, the setting of the user priority may be such that the data has the best transmission priority when the delay time exceeds a prescribed time.

Alternatively, the setting of the user priority may be that, if the delay time exceeds a prescribed time, a user priority higher than the user priority determined by the property of the data may be set in the data. .

And the present invention, the step of calculating the delay time using the transmission time information included in the received data; Storing the received data in a corresponding data buffer in consideration of the delay time and the user priority of the received data; And transmitting data selected from at least one data buffer through a contention scheme.

In this case, the present invention may further include storing a transmission time in the data when the data is transmitted.

The storing of the data in the data buffer may include storing the data in a data buffer whose transmission priority is increased or decreased from the data buffer corresponding to the user priority according to the delay time.

Alternatively, storing the data in the data buffer may include storing the data in a data buffer having the best transmission priority when the delay time exceeds a prescribed time.

Alternatively, storing the data in the data buffer may include storing the data in a data buffer having a higher transmission priority than the data buffer corresponding to the user priority when the delay time exceeds a predetermined time. It may be to save.

On the other hand, the present invention comprises the steps of storing the received data in a data buffer corresponding to the user priority; Accessing a transmission medium to transmit data stored in at least one data buffer; If data stored in two or more data buffers are to be transmitted at the same time, the data of the wireless communication comprising the step of determining and transmitting the data to be transmitted first considering the user priority of each data and the delay time of each data It includes a transmission method.

In this case, the transmission data may be determined by modifying a user priority of each data in consideration of the delay time and comparing the modified user priorities.

Here, the modification of the user priority may be performed by dividing the delay time into a plurality of groups, putting an added value to each group, and correcting the user priority according to the added value.

Alternatively, the determination of the transmission data may be determined to preferentially transmit data in which the delay time exceeds a prescribed time when there is data in which the delay time exceeds a prescribed time.

According to the present invention having the configuration as described above, when scheduling the transmission order of the frame, the transmission delay time information of the frame is taken into consideration, there is an advantage that can prevent the waste of radio resources caused by the delay of the retransmission of the frame. .

The present invention includes a delay time of a transmission frame in determining a contention-based channel access priority for guaranteeing QoS (Quality of Service) of wireless communication, although the scope of the present invention is not limited to the contents of the IEEE 802.11e standard. For convenience of description, a specific embodiment will be described as an example applied in wireless communication according to the IEEE 802.11e standard.

Hereinafter, a specific embodiment of a wireless communication system and a frame transmission method thereof according to the present invention as described above will be described in detail with reference to the accompanying drawings.

In the following, first, a schematic description of wireless communication defined in IEEE 802.11 and an EDCA scheme in which the present invention is implemented will be described in detail.

FIG. 1 is a schematic diagram illustrating an EDCA channel approach scheme, FIG. 2 is a schematic diagram illustrating a competition state for each AC within a station in an EDCA scheme, FIG. 3 is a schematic diagram illustrating EDCA TXOP bursting, and FIG. 5 is a block diagram showing a structure of an ACK frame, FIG. 5 is a block diagram showing a MAC header region of a transport frame according to a specific embodiment of the present invention, and FIG. 6 is a frame transmission method according to the first embodiment of the present invention. 7 is a flowchart illustrating a frame transmission method according to the second and third embodiments of the present invention, and FIG. 8 illustrates a frame transmission method according to the fourth and third embodiments of the present invention. It is a flow chart.

To provide more advanced QoS in a wireless LAN, an 802.11e MAC is provided that complements the existing 802.11 MAC.

 IEEE 802.11e defines a new wireless LAN MAC protocol that can transmit delay-sensitive traffic in addition to the best effort service by defining EDCA and HCCA that can support QoS at the wireless LAN MAC layer based on the DCF transmission method of 802.11 MAC. to provide.

802.11e defines the Hybrid Coordination Function (HCF) based on the existing 802.11 MAC protocols DCF and PCF. HCF includes new media access mechanisms to improve the QoS of wireless LANs and can transmit QoS data in both contention and contention-free cycles. In the following description, a QoS STA (QSTA: QoS Station) expressed in 802.11e refers to a station supporting QoS, and a QoS AP (QAP: QoS AP) refers to an access point supporting QoS.

The HCF has two modes of operation, one is contention-based Enhanced Distributed Channel Access (EDCA) and the other is HCCA controlled channel access (HCCA) using a non-competitive channel approach using a polling mechanism. to be.

The EDCA and HCCA are controlled by a hybrid coordinator (HC) located in an access point (hereinafter referred to as an 'AP'), and are also compatible with existing 802.11 MACs using DCF and PCF. The EDCA provides Prioritized Traffic similar to DiffServ in a wired network for QoS support (Supported QOS), while the HCCA provides Parameterized Traffic similar to IntServ for Garanteed QoS. do.

The EDCA scheme is used to support priority-based QoS in infrastructure and ad hoc modes. That is, the EDCA provides differentiated channel access function for frames having different priorities from higher layers, while the HCCA provides parameter-based QoS in infrastructure mode.

The 802.11e MAC establishes a virtual connection called a traffic stream between two stations (hereinafter referred to as 'STA') prior to transmitting data to provide parameter QoS. Parameters that require the characteristics of the data to be actually transmitted and QoS go through trade-offs and exchanges in setting up the traffic stream. The AP allocates a radio band to each STA based on the exchanged QoS parameters and performs frame transmission scheduling for polling frame and downlink frame transmission.

Transmission Opportunity (TXOP) of the 802.11e MAC is used to give a certain time for transmitting a frame to a specific STA and to ensure this. TXOP acquisition is made possible by either succeeding in EDCA competition or by receiving a QoS CF-Poll frame from the AP, the former is called EDCA TXOP and the latter is called folded TXOP.

As described above, a certain time may be given or a transmission time may be forcibly limited by any one STA to transmit a frame using the TXOP. The transmission start time and the maximum transmission time of the TXOP are determined by the AP. The STACA is informed by the beacon frame in the case of the EDCA TXOP and the QoS CF-Poll frame in the case of the fold TXOP.

The EDCA is used only in the competition period while the HCCA can theoretically operate in both the competition and non-competition periods, but is preferably used only in the competition period.

Hereinafter, first, the EDCA method will be described.

As described above, EDCA, a contention-based channel approach, augments the existing DCF to allow differentiated media access for frames with eight types of user priorities. In Table 1 below, an example of a user priority table is summarized in a table (Table 1 shows a user priority table by IEEE 802.1D). Each frame arriving from the upper layer to the MAC layer has a specific user priority value, and each QoS data frame MAC header carries a user priority value.

User Priority and AC Response Table User priority 802.1D Designation AC (Access Category) Designation One BK AC_BK Back ground 2 - AC_BK Back ground 0 BE AC_BE Best effort 3 EE AC_BE Best effort 4 CL AC_VI Video 5 VI AC_VI Video 6 VO AC_VO Voice 7 NC AC_VO Voice

For the transmission of QoS data frames including these priorities, the 802.11e QoS STA implements four access categories (AC) (see Table 1). The user priority of frames arriving at the MAC layer is assigned to one AC corresponding to each other. The user priorities in Table 1 above are specified in the IEEE 802.1D bridge standard. Every AC has its own transmit queue and AC parameters, and the difference in priority between ACs is implemented from differently set AC parameter values.

Basically, EDCA uses AIFS [AC], CWmin [AC], CWmax [AC] instead of DIFS, CWmin, CWmax which DCF uses in competition to transmit frames belonging to AC. AIFS [AC] is determined by SIFS + AIFS [AC] slot time, where AIFS [AC] is an integer greater than zero.

When the collision between STAs occurs during frame transmission, the EDCA backoff process of generating a new backoff counter is similar to the existing DCF. The EDCA adds a 'Persistence Factor' that is assigned differently for each AC. If the PF value is 2, the CW (Contention Window) size increases exponentially as in DCF.

As shown in FIG. 1, the channel approach of the EDCA is similar to that of DCF. However, each AC maintains a different Arbitration Inter Frame Space (AIFS) and CW. In this case, AIFS should be larger than PIFS and DIFS. This is to set at least larger than SIFS time to protect transmission of ACK frame.

Values such as AIFS [AC], CWmin [AC], CWmax [AC], etc., referred to as the EDCA parameter set, may be notified to each STA in a beacon frame by the AP. Basically, the smaller the value of AIFS [AC] and CWmin [AC], the higher the priority. Therefore, the shorter the channel access delay, the more bandwidth is used in a given traffic environment.

The EDCA parameters are an important means used to differentiate channel access in various user priority traffic. In addition, proper setting of EDCA parameter values, including parameters for each AC, optimizes network performance while delivering traffic prioritized. Therefore, the AP needs to perform overall management and coordination functions for the EDCA parameters to ensure fair access to all STAs participating in the network.

As shown in FIG. 2, four AC-specific transmission queues defined in the 802.11e MAC serve as individual EDCA competition entities for wireless medium access within one STA. An AC maintains its own backoff counter with its AIFS value. If there is more than one AC that has been backed off at the same time, the collisions between the ACs are handled by the Virtual Collision Handler. The highest priority frame is selected first and transmitted for competition between STAs, and the other ACs increase the CW value to update the backoff counter again.

 As mentioned above, 802.11e determines a transmission time based on TXOP when a specific STA starts transmission. The 802.11e AP carries EDCA parameters such as AIFS [AC], CWmin [AC], CWmax [AC], and TXOP Limit [AC], which is an EDCA TXOP time, in a beacon frame and delivers them to each STA.

As shown in FIG. 3, during the EDCA TXOP Limit time, several frames may be simultaneously transmitted in an SIFS interval between ACK and continuous frame transmission. Thus, transmitting several frames simultaneously is called 'EDCA TXOP bursting.' '

Two QoS data frames including the priority are transmitted during the TXOP Limit time, and it can be seen that two QoS data frames and the ACK frame are transmitted within the TXOP Limit time determined by the AP. EDCA TXOP bursting does not affect the performance of the entire network by EDCA TXOP bursting because the TXOP Limit must be observed when transmitting multiple frames. Therefore, selecting the appropriate TXOP Limit value can improve overall network performance.

On the other hand, in the EDCA communication, when the final destination of the frame is set (i.e., not the multicast transmission method, but the transmission destination of the transmission data is specified), the receiving STA receiving the frame is sent to the transmitting STA. An acknowledgment frame (ACK frame) is transmitted to indicate that the frame has been received.

The response frame is used for transmission of all frames, such as a simple transmission frame, a fragmented frame, a frame following an RTS / CTS exchange, and the structure thereof is approximately as shown in FIG.

As shown in the figure, an ACK frame includes a frame control field, a persistent field, and a reception address field.

The frame field indicates that the frame is an ACK frame and has a size of 2 bytes.

The persistence field indicates whether there is data after succession, and the ACK for the last fragment in the transmission data frame or the fragment burst indicates that there is no subsequent data frame since the duration is set to 0, and the continuous frame is If present, it indicates that there is a frame transmitted continuously with the ACK frame as 1.

In addition, the reception address field indicates an address of a destination to which the ACK frame is to be transmitted. The source address of the transmitted data frame is copied and stored.

Hereinafter, a specific embodiment of the present invention will be described.

According to the present invention, a transmission frame includes a delay parameter in the MAC header portion. In this case, the transmission frame includes both a data frame and a control frame. Hereinafter, for convenience of description, the transmission frame will be described as an example.

5 shows a data frame according to the present invention.

As shown, the MAC header of the data frame includes Frame control, Duration ID, Address 1, Address 2, Address 3, Sequence Control, Address 4, QoS control and delay parameters.

Here, the location of the delay parameter is only an example, it can be apparent that it can be provided at various locations according to the characteristics and structure of the transmission frame.

The delay frame is a portion for storing a transmission time when the first data frame is transmitted, and when there is a request for retransmission for the data frame, the delay time may be stored after calculating the delay time using the transmission time. Part.

First Embodiment

6 is a flowchart illustrating a frame transmission method according to the first embodiment of the present invention.

As shown, when the frame is transmitted according to the first embodiment of the present invention, first, the transmission time is stored in the transmission frame to be transmitted (S110). At this time, the transmission time is stored in the delay parameter area provided in the MAC header portion of the transmission frame (of course, the transmission time may be stored in other areas).

Thereafter, the transmitting station transmits the transmission frame (S120).

After transmission of the transmission frame, the transmission station determines whether an ACK frame has been received from the reception station within a specified time (S130).

The ACK frame is a frame for informing the transmitting station that the receiving station receives the transmission frame after receiving the transmission frame.

Therefore, a transmission frame that has not received the ACK frame within the designated time assumes that the transmission frame has not been transmitted, and retransmits the transmission frame.

At this time, the user priority of the transmission frame is set using the delay parameter of the retransmitted transmission frame (S140).

According to the first embodiment of the present invention, the delay time is calculated by comparing the transmission time stored in the delay parameter with the current time. In this case, the delay time may be defined as a time from the transmission time to the current time, and it is determined that the delay time is not delayed until the time defined as the default value from the transmission time, and only the time after the default value is set as the delay time. It is also possible. This is to prevent the user priority of the transmission data from being excessively modified by the delay time.

Therefore, it is possible to set the default value that should be small in the case of data where prevention of delay is important (for example, data in which reception of continuous data is important), and to set the default value large in the case of data that is not significantly affected by delay. have.

ms 미만인 경우 IEEE 208. 1D 규격에 의한 사용자 우선순위를 그대로 적용하고, 상기 지연 시간이

ms 내지

ms 인 경우에는 상기 사용자 우선 순위를 1 단계 상승하며, 상기 지연 시간이

ms 내지

ms 인 경우에는 상기 사용자 우선순위를 2 단계만큼 상승시킨다. The user priority is increased in proportion to the delay time in consideration of the delay time. That is, the delay time

If less than ms, the user priority according to IEEE 208 1D standard is applied as it is, and the delay time is

ms to

If ms, the user priority is increased by one step, and the delay time is

ms to

In the case of ms, the user priority is increased by two levels.

The above example merely illustrates an increase of the user priority, and a reference value of the increase of the user priority may be variously applied.

An access category (AC) is determined according to the user priority of the transmission frame to be retransmitted with the user priority set (S150).

If the AC is determined, transmits a transmission frame to a transmission queue corresponding to the determined AC (S160), and transmits to a receiving station. At this time, the transmission frame is transmitted without setting the transmission time in the retransmitted frame. This is because, if the ACK frame for the retransmitted transmission frame is not received again and the retransmission is attempted, it is effective for the transmitting station to calculate the delay time from the initial transmission time and reflect it in the user priority determination. Because.

Second Embodiment

7 is a flowchart illustrating a frame transmission method including the second and third embodiments of the present invention. Here, the first to third embodiments of the present invention have a common content of setting a transmission queue using a delay time of a transmission frame.

The second embodiment of the present invention follows the same flow as shown, except for the method of determining AC using the delay parameters (S240, 250) as the first embodiment of the present invention.

That is, in the second embodiment of the present invention, the delay time may be calculated, the delay time may be changed to a prescribed grade, and the grade may be stored in the delay parameter. Thus, the delay parameter stores the transmission time and delay class stored during the initial transmission.

In the second embodiment of the present invention, user priority is determined by IEEE 802.1D (S240). That is, the user priority is determined by the nature of the original frame, and in determining the AC, the AC and the transmission queue are determined in consideration of the delay class included in the delay parameter (S250).

In this case, as described above, the delay level may be updated and increased when retransmission is repeated.

Third embodiment

The third embodiment of the present invention also has the same flow except for the first step of the present invention and the first step of determining user priority using delay parameters.

 That is, in the third embodiment of the present invention, the delay time is calculated from the stored transmission time, and it is determined whether the delay time exceeds the prescribed time. If the delay time exceeds the prescribed time, the transmission frame is allocated to a transmission queue corresponding to the best user priority.

Therefore, in the third embodiment, only the transmission queue is newly allocated using the delay time without having to modify the user priority.

In this case, as described above, the transmission queue may be allocated to the highest queue when the delay time exceeds a prescribed time, and may be allocated to the transmission queue having a higher priority than the transmission queue to be originally allocated. Method is also possible.

8 is a flowchart illustrating a frame transmission method according to the fourth and fifth embodiments of the present invention. In the fourth and fifth embodiments of the present invention, it is common to use a delay time of a transmission frame to select a transmission frame when an internal collision between ACs occurs.

Fourth Embodiment

As shown, when the frame is transmitted according to the fourth embodiment of the present invention, first, the transmission time is stored in the transmission frame to be transmitted (S310). In this case, the transmission time is as described in the description of the first embodiment of the present invention.

Thereafter, the transmitting station transmits the transmission frame (S320).

After the transmission of the transmission frame, the transmitting station determines whether an ACK frame has been received from the receiving station within a predetermined time (S330).

A transmission frame that has not received the ACK frame within the specified time considers that the transmission frame has not been transmitted and retransmits the transmission frame.

To this end, the transmission frame is determined according to the user priority (AC) (S340).

When the AC is determined, the transmission frame is transmitted to the transmission queue corresponding to the determined AC (S350) and transmitted to the receiving station.

Thereafter, it is determined whether internal collision between AC has occurred (S360). If the collision between the AC has not occurred, the transmission data is transmitted in the transmission order of the transmission queue.

However, when there is an internal collision between ACs, the virtual collision handler selects and transmits a frame having a high user priority among frames contained in the AC which caused the collision. According to the fourth embodiment of the present invention, the virtual collision handler has a delay time. The frame is selected using the information (S370).

That is, after changing the user priorities by the method described in the first embodiment of the present invention, these changed user priorities are compared to select and transmit a transmission frame having a high user priority.

The transmission frame selected in this way is transmitted to the receiving station (S380).

In this case, too, the transmission frame is transmitted without setting the transmission time in the retransmitted frame. The reason for this is as described above.

Fifth Embodiment

The fifth embodiment of the present invention follows the same flow except for the fourth embodiment of the present invention and the method in which the virtual collision processor selects a transmission frame.

That is, in the fifth embodiment of the present invention, when the collision between ACs occurs, the virtual collision processor examines the frame causing the collision and determines whether there is a frame whose delay time exceeds the threshold. Here, the threshold value is a delay time value that can be considered that abnormal delay has occurred in the wireless LAN communication, and may be appropriately set according to the environment of the communication.

At this time, if no frame exceeds the threshold, the user priority is compared (the user priority refers to the user priority without taking into account the delay time), and the transmission frame is selected. If there is a transmission frame having, the frame is transmitted first.

This is to allow the delayed data to be transmitted first in order to prevent data flow and resource waste when the transmission time is greatly delayed.

In the present specification, a specific embodiment of the present invention has been described, and a station is divided into a transmitting station and a receiving station.

In the transmission of a general data frame, the AP will act as a transmitting station, and the terminal will act as a receiving station.

However, in the case of data transmitted from the terminal device to the AP, the terminal device will be the transmitting station, and the AP will be the receiving station.

In addition, in the ad-hoc mode in which the terminal and the terminal are connected rather than the infrastructure mode in which the AP and the terminal are connected, both the transmitting station and the receiving station will be the terminal.

The rights of the present invention are not limited to the embodiments described above, but are defined by the claims, and those skilled in the art can make various modifications and adaptations within the scope of the claims. It is self-evident.

In the wireless communication system and the frame transmission method according to the present invention as described in detail above, the following effects can be expected.

That is, since the frame transmission order is scheduled in consideration of the delay time information of the transmitted frame, the retransmitted frame (hence, the delay time is considerably higher than the first transmitted frame) can be transmitted first. Therefore, the probability of completing the retransmission in the state where the receiving terminal occupies the medium increases. Therefore, after the receiving terminal finishes occupying the medium, the fragment frame to be retransmitted is not transmitted, and thus there is a low risk of competing to occupy the medium again, thereby avoiding wasting radio resources.

In addition, in the present invention, when the retransmission request for a frame is repeated (when the transmission frame does not arrive at the destination repeatedly), delay time information is accumulated and increases, and accordingly, the transmission priority is accumulated and increased so that retransmission is repeated. There is an advantage that can be transmitted preferentially the frame.

Claims (50)

A transmission station storing a transmission time in a transmission frame, calculating a delay time using the transmission time when a transmission frame is requested, and scheduling transmission of the transmission frame using the delay time; And a receiving station for transmitting an ACK frame to the transmitting station when the transmission frame is received. The method of claim 1, The transmission time is, And a delay parameter area provided in a MAC header portion of the transmission frame. The method of claim 2, Scheduling of the transmission frame, Dividing a certain time range into a plurality of groups, putting each value in each group, And the delay time is performed based on the modified user priority by modifying the user priority according to the added value of the corresponding group. The method of claim 3, wherein If the modified user priority is less than zero, set the user priority to zero; And if the modified user priority is greater than seven, set the user priority to seven. The method of claim 2, Scheduling of the transmission frame, Set and store the delay level from the delay time, AC is determined primarily by user priority, and AC is adjusted in consideration of the delay level to set a final AC to which the transmission frame belongs. The method of claim 2, Scheduling of the transmission frame, It is determined whether the delay time exceeds a prescribed time, and if the delay time exceeds the prescribed time, the transmission frame is assigned to a transmission queue corresponding to the best user priority so that the transmission is made preferentially. Wireless communication system. The method of claim 2, Scheduling of the transmission frame, It is determined whether the delay time exceeds a prescribed time, and if the delay time exceeds the prescribed time, a transmission queue having a higher priority than the transmission queue corresponding to the user priority of the transmission frame. Wireless communication system, characterized in that to be transmitted to. The method according to any one of claims 1 to 7, And wherein the transmitting station is an access point and the receiving station is a terminal device. The method according to any one of claims 1 to 7, And the transmission frame is a QoS data frame. The method according to any one of claims 1 to 7, The wireless communication is in an ad-hoc mode, And the transmitting station and the receiving station are terminal devices. A transmission station storing a transmission time in a transmission frame, and selecting a frame to be transmitted using a delay time calculated from the transmission time in case of a collision between ACs; And a receiving station for transmitting an ACK frame to the transmitting station when the transmission frame is received. The method of claim 11, wherein The virtual collision handler, Dividing the predetermined time range into a plurality of groups, adding or subtracting a value range to each group, and modifying the user priority defined by the priority table according to the value of the group corresponding to the delay time; And comparing the modified user priorities, selecting and transmitting the frame having the highest modified priority. The method of claim 11, wherein The virtual collision processor, Determine whether the delay time exceeds a threshold, And when there is a transmission frame having a delay time exceeding the threshold value, selecting and transmitting the transmission frame as the highest priority. Storing the received data in a corresponding data buffer according to a user priority; Storing a transmission time when transmitting the stored data; When transmitting the data, driving a timer to determine whether a response signal to the transmitted data is received before the timer reaches a specific value; Calculating a delay time for the data using the stored transmission time when the timer reaches a specific value without receiving the response signal; And And setting a user priority for the data using the calculated delay time, storing the data in a data buffer corresponding to the user priority, and then attempting to retransmit the data. Transmission method. The method of claim 14, The user priority is, And is set when data to be transmitted is transmitted from a higher layer to a MAC layer, and is stored in a MAC header portion of the data. The method of claim 14, The transmission time is, The data transmission method of the wireless communication, characterized in that stored in the delay parameter area provided in the MAC header portion of the data. The method of claim 14, The delay time is, If the measured value of the timer is less than the default value is set to 0, If the measured value of the timer exceeds the default value, the data transmission method of the wireless communication, characterized in that exceeding the default value. The method according to any one of claims 14 to 17, The setting of the user priority is, The delay time is divided into a plurality of groups, each group is added or subtracted, And the user priority determined by the property of the data is set by modifying the delay according to the value of the group corresponding to the delay time. The method according to any one of claims 14 to 17, The setting of the user priority is, And if the delay time exceeds a prescribed time, the data is set to have the best transmission priority. The method according to any one of claims 14 to 17, The setting of the user priority is, And if the delay time exceeds a prescribed time, user data higher than the user priority determined by the property of the data is set to the data. In a contention-based channel approach to improve the quality of service of wireless communication, (A) storing a transmission time in a transmission frame to be transmitted; (B) transmitting the transmission frame; (C) checking whether a response frame is received within a designated time; (D) if the response frame is not received within a specified time, calculating a delay time from the transmission time, and setting a user priority of the transmission frame using the delay time; (E) determining an access category (AC) according to the set user priority; And And (F) transmitting the transmission frame to the transmission queue corresponding to the AC. The method of claim 21, The setting of the priority of the step (D), Dividing a certain time range into a plurality of groups, putting each value in each group, And setting and modifying the user priority set by the priority table according to the added / decreased value of the group corresponding to the delay time. The method of claim 22, (D ') setting the user priority to zero when the user priority is less than zero; (D '') if the user priority is greater than 7, further comprising the step of setting the user priority to seven. The method of claim 23, And said transmitting station is an access point and said receiving station is a terminal device. The method of claim 23, And the transmission frame is a QoS data frame. The method according to any one of claims 21 to 25, The wireless communication is in an add-hoc mode, and the transmitting station and the receiving station are terminal devices. Calculating a delay time using transmission time information included in the received data; Storing the received data in a corresponding data buffer in consideration of the delay time and the user priority of the received data; And And transmitting data selected from at least one data buffer by a contention method. The method of claim 27, And storing the transmission time in the data when transmitting the data. The method of claim 28, The transmission time is, And storing the delay parameters in the MAC header portion of the data. The method of claim 29, The user priority is, And is set when data to be transmitted is transmitted from a higher layer to a MAC layer, and is stored in a MAC header portion of the data. The method of claim 27, The delay time is, If the measured value of the timer is less than the default value is set to 0, If the measured value of the timer exceeds the default value, the data transmission method of the wireless communication, characterized in that exceeding the default value. The method according to any one of claims 27 to 31, The storing of the data in the data buffer may include: And storing the data in a data buffer whose transmission priority is increased or decreased than the data buffer corresponding to the user priority according to the delay time. The method according to any one of claims 27 to 31, The storing of the data in the data buffer may include: And when the delay time exceeds a prescribed time, storing the data in a data buffer having the best transmission priority. The method according to any one of claims 27 to 31, The storing of the data in the data buffer may include: And if the delay time exceeds a prescribed time, storing the data in a data buffer one transmission priority higher than the data buffer corresponding to the user priority. In a contention-based channel approach to improve the quality of service of wireless communication, (a) storing a transmission time in a transmission frame to be transmitted; (b) transmitting the transmission frame; (c) checking whether a response frame is received within a designated time; (d) if the response frame is not received within a specified time, setting a user priority of the transmission frame according to a priority table; (e) determining an access category (AC) of the transmission frame using a delay time calculated based on the user priority and the transmission time; And (f) transmitting a transmission frame to a transmission queue corresponding to the AC. 36. The method of claim 35 wherein In the step (e) the determination of AC, Calculating a delay level corresponding to the delay time and determining an AC to which the transmission frame belongs according to the delay level. 36. The method of claim 35 wherein In the step (e) the determination of AC, Determine whether the delay time exceeds a prescribed time, And if the delay time exceeds a prescribed time, set the transmission frame to belong to the highest AC. 36. The method of claim 35 wherein In the step (e) the determination of AC, Determine whether the delay time exceeds a prescribed time, If the delay time exceeds the prescribed time, the data transmission of the wireless communication characterized in that for transmitting the transmission frame to the AC having a higher priority than the AC corresponding to the user priority of the transmission frame Way. The method according to any one of claims 35 to 37, The transmission time is, And a delay parameter area provided in a MAC header portion of the transmission frame. Storing the received data in a data buffer corresponding to a user priority; Accessing a transmission medium to transmit data stored in at least one data buffer; When data stored in two or more data buffers are to be transmitted at the same time, determining and transmitting the data to be transmitted first considering the user priority of each data and the delay time of each data, characterized in that it comprises the step of transmitting Data transmission method of wireless communication. The method of claim 40, And storing the transmission time in the data when transmitting the data. 42. The method of claim 41 wherein The transmission time is, The data transmission method of the wireless communication, characterized in that stored in the delay parameter area provided in the MAC header portion of the data. 42. The method of claim 41 wherein The user priority is, And is set when data to be transmitted is transmitted from a higher layer to a MAC layer, and is stored in a MAC header portion of the data. 42. The method of claim 41 wherein The delay time is, If the measured value of the timer is less than the default value is set to 0, If the measured value of the timer exceeds the default value, the data transmission method of the wireless communication, characterized in that exceeding the default value. The method according to any one of claims 40 to 44, The determination of the transmission data, And determining the user priority of each data by considering the delay time and comparing the modified user priorities. The method of claim 45, The modification of the user priority, And dividing the delay time into a plurality of groups, adding a value to each group, and modifying the user priority according to the added value. The method according to any one of claims 40 to 44, The determination of the transmission data, And when the delay time exceeds the prescribed time, it is determined to preferentially transmit the data exceeding the prescribed time. In a contention-based channel approach to improve the quality of service of wireless communication, (I) storing a transmission time in a transmission frame to be transmitted; (II) transmitting the transmission frame; (III) detecting whether an internal collision between ACs has occurred; (IV) when the internal collision occurs, selecting, by the virtual collision processor, a frame to be transmitted in consideration of the transmission time; (V) The data transmission method of the wireless communication comprising the step of transmitting the set frame. 49. The method of claim 48 wherein In step (IV), the transmission frame is selected. Dividing the predetermined time range into a plurality of groups, adding or subtracting the respective time ranges, and modifying the user priority defined in the priority table according to the group value of the corresponding delay time; Comparing the modified user priorities, selecting and transmitting a frame having the highest modified priority. 49. The method of claim 48 wherein In step (IV), the transmission frame is selected. Determine whether the delay time exceeds a threshold, And if there is a transmission frame having a delay time exceeding the threshold, selecting and transmitting the transmission frame as the highest priority.

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